Full-contour Y-TZP ceramic surface roughness effect on synthetic hydroxyapatite wear

ObjectiveTo investigate the effects of polishing techniques on the surface roughness of Y-TZP ceramic and on the wear behavior of synthetic hydroxyapatite (HA).MethodsThirty-two full-contour Y-TZP (Diazir®) sliders (φ = 2 mm × 1.5 mm in height) were manufactured using CAD/CAM, embedded in acrylic resin using brass holders, and randomly allocated into four groups (n = 8): according to the finishing/polishing procedure: G1-as-machined, G2-glazed, G3-diamond bur finishing and G4 − G3 + OptraFine® polishing kit. Thirty-two sintered HA disks (φ = 13 mm × 2.9 mm in height) were similarly mounted in brass holders. Y-TZP sliders baseline surface roughness values (Ra and Rq, in μm) were recorded using a non-contact profilometer (Proscan 2000). A two-body pin-on-disc wear test was performed. HA height (μm) and volume (mm3) losses were measured. Y-TZP height loss was measured using a digital micrometer. One-way ANOVA was used to determine the effect of the polishing techniques on the surface roughness. Comparisons between groups for differences in antagonist height loss/volume, and slider height loss were performed using one-way ANOVA. Statistical significance was set at α = 0.05.ResultsRoughness measurements showed significant differences (p = 0.0001) among the surface treatments with G1 (Ra = 0.84, Rq = 1.13 μm) and G3 (Ra = 0.89, Rq = 1.2 μm) being the roughest, and G2 (Ra = 0.42, Rq = 0.63 μm) the smoothest (p = 0.0001). Y-TZP slider height loss was highest for the glazed group (35.39 μm), and was lowest for the polished group (6.61 μm) (p = 0.0001). Antagonist volume and height losses for groups (G1–G3) were similar, while the polished group (1.3 mm3, 14.7 μm) showed significant lower values (p = 0.0001).SignificanceAlthough glazed zirconia provides an initially smooth surface, significantly increased antagonist wear was observed compared to the polished Y-TZP zirconia surface.